fix: Improve workspace comment keyboard navigation behavior.

[gonfunko]

The basics

• I validated my changes

The details

This PR addresses two points of feedback raised in RaspberryPiFoundation/blockly-keyboard-experimentation#625:

• The workspace comment textarea has its tabindex set to -1, preventing tabbing into it. It remains accessible via keyboard navigation.
• When workspace comments are focused, they will be scrolled into view on the workspace.

[maribethb]

lgtm when tests pass. though i don't think the current approach to scrolling into view is very nice, that is a long term problem to fix.

do you think we need an interface for "Scroll-into-view-able"?

or should these components do this automatically in their "onNodeFocus" methods? is there a time when a node is focused that we wouldn't want to scroll them into view?

these are just rhetorical questions for now. i'll file an issue for them.

[gonfunko]

Thanks! I don't think the test failures are actually related to this PR - they pass locally, and nothing in this would make Blockly.getMainWorkspace() not be a function.

[maribethb]

Thanks! I don't think the test failures are actually related to this PR - they pass locally, and nothing in this would make Blockly.getMainWorkspace() not be a function.

fair, i didn't investigate what the failures actually were